1. Field of the Invention
The present invention relates to a variable compression ratio mechanism capable of changing the compression ratio of an internal combustion engine by changing the volume of each combustion chamber thereof.
2. Description of the Related Art
In recent years, there have been proposed techniques capable of changing the compression ratio of an internal combustion engine for the purpose of improving fuel mileage performance, output performance, etc. As such kinds of techniques, there has been proposed one in which a cylinder block and a crankcase are coupled with each other, and camshafts are mounted on the coupling portions thereof, respectively, in such a manner that the compression ratio of the engine is changed by rotating the camshafts so as to move the cylinder block and the crankcase toward and away from each other (for example, see a first patent document: Japanese patent application laid-open No. 2003-206771). A second patent document (Japanese patent application laid-open No. 7-26981) is also cited as a reference document relevant to such a technique.
In the above-mentioned prior art, loads resulting from combustion or firing pressure, the self weight of the cylinder block and the like act between the camshafts and the bearing portions for rotatably supporting the camshafts. In addition, the camshafts in the above-mentioned prior art are not driven to rotate at high speed and at all times during engine operation as the camshafts in the crankshafts or the valve systems.